1. Field of Invention
The present invention relates to a display device for displaying characters, numbers, patterns, or the like. The present invention also relates to an electronic timepiece, such as a wristwatch or a stopwatch, for giving or measuring time.
2. Description of Related Art
Conventionally, there are widely known display devices which utilize flat displays, such as liquid crystal displays, for displaying numbers, characters, or other information. For example, as shown in FIG. 9, in an electronic timepiece utilizing a liquid crystal display, a pair of polarizers 52 and 53 are placed on both sides of a liquid crystal panel 51, and a light-emitting element 54 is disposed at the back side of the polarizer 53. The pair of polarizers 52 and 53 are disposed such that, for example, their azimuthal angles are set to form a right angle.
During daytime, conventional electronic timepieces display numerical information or the like using external light, whereas during the night they display numerical information or the like using light emitted from the light-emitting element 54, when necessary. Numerical information or the like is displayed by applying a predetermined voltage between the electrodes of the liquid crystal panel 51, with the area to which voltage is not applied appearing as a white background or the like. In the figure, the area to which a voltage is applied to display information is represented as ON, whereas the background color area to which a voltage is not applied is represented as OFF.
As indicated by arrow P, when external light is used to produce background color of a display (liquid crystal panel is turned off), the linearly polarized light component of the external light or natural light, which is oriented parallel to the plane of the figure, passes through the polarizer 52. Then, the polarization direction thereof is twisted 90 degrees by the liquid crystal panel 51 in an off state, causing the linearly polarized light to be oriented perpendicular to the plane of the figure. The linearly polarized light, which has passed through the polarizer 53, is irregularly reflected by a surface of the light-emitting element 54, and part of the irregularly reflected light is transmitted successively back through the polarizer 53, the liquid crystal panel 51, and the polarizer 52 to produce a white background which is perceived by any viewer.
As indicated by arrow Q, when numerical information or the like is to be displayed using external light (the liquid crystal panel 51 is turned on), linearly polarized light, which is oriented parallel to the plane of the figure, is separated from the external light by the polarizer 52, and passes through the liquid crystal panel 51. Since the liquid crystal panel 51 is in an on state, the polarization direction of the linearly polarized light is maintained parallel to the plane of the figure, so that it is absorbed by the polarizer 53. The portion that has absorbed the light appears black to any viewer.
As can be understood from the foregoing description, when external light is used, numbers or the like are displayed on a background having a color corresponding to that reflected from the light-emitting element 54 in order to display the time or other information.
On the other hand, as indicated by arrow C, when a background color is to be produced using light emitted from the light-emitting element 54 (the liquid crystal panel 51 is turned off), the linearly polarized light which is oriented perpendicular to the plane of the figure is separated from randomly polarized light emitted from the light-emitting element 54 by the polarizer 53. Since the liquid crystal panel 51 is in an off state, the polarization direction of the linearly polarized light is twisted 90 degrees by the liquid crystal panel 51, causing the linearly polarized light to be oriented parallel to the plane of the figure. Then, the polarized light passes through the polarizer 52 and is perceived by an outside viewer. The perceived color is the color emitted from the light emitting element 54, which is ordinarily white.
As indicated by arrow D, when numerical information or the like is to be displayed using light emitted from the light emitting element 54 (the liquid crystal panel 51 is turned on), the linearly polarized light, which is oriented perpendicular to the plane of the figure is separated from the light emitted from the light emitting element 54 by the polarizer 53, passes through the liquid crystal panel 51 in an on state, and reaches the polarizer 52. Here, the polarization direction of the linearly polarized light does not match the polarization direction of the polarizer 52, so that the linearly polarized light is absorbed by the polarizer 52. The portion of the polarizer which has absorbed the light, appears black to any viewer.
As can be understood from the foregoing description, when light from the light-emitting element 54 is used, numbers or the like are displayed in black or the like on a background having a color corresponding to the color emitted from the light emitting element 54.
In the above-described conventional electronic timepiece, two polarizers 52 and 53 are disposed on both sides of the liquid crystal panel 51. These polarizers are capable of absorbing linearly polarized light other than that having a predetermined polarization direction. Therefore, the intensity of the light, emitted to the outside for producing a background color or displaying numerical information or the like, may be greatly reduced, causing numerical information or the like to appear dark, and thus difficult to read.
Theoretically speaking, various background colors can be produced, or numerical information or the like can be displayed in various colors by providing a color filter, producing the right color, at a surface of the light-emitting element 54. Actually, however, various display colors cannot be produced, since the light intensity is greatly reduced, so that either a bright, white color or gray had to be used for the display.